按季度计算日期

Question

我正在寻找一种简单而有效的Objective-C算法，该算法从一年的特定季度（3个月）开始，增加或减少特定数量的宿舍。

例如，2012年第一季度增加了10个季度，我得到的年份为：2012 +楼层（10/4）= 2012 + 2 = 2014，则季度：1 + Mod（10，4）= 1 + 2 = Q3。从2011年第三季度减去2季度，我想最终与2011年第一季度。

什么是最优雅的代码来完成这一点？

Answer 1

- (void)addQuarters:(NSInteger)quarters toYear:(NSInteger *)currentYear andQuarter:(NSInteger *)currentQuarter { 
    if (*currentYear < 0 || 
     *currentQuarter < 1 || 
     *currentQuarter > 4) { 
     return; 
    } 

    *currentYear += quarters/4; 
    *currentQuarter += quarters % 4; 

    if (*currentQuarter > 4) { 
     *currentQuarter -= 4; 
     *currentYear += 1; 
    } else if (*currentQuarter < 1) { 
     *currentQuarter += 4; 
     *currentYear -= 1; 
    } 
} 

// Example of use: 
NSInteger year = 2012; 
NSInteger quarter = 2; 

[self addQuarters:-7 toYear:&year andQuarter:&quarter]; 
NSLog(@"Quarter %i of %i", quarter, year); 
// Output: Quarter 3 of 2010 

Answer 2

代码从这里改变：

https://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/DatesAndTimes/Articles/dtCalendricalCalculations.html#//apple_ref/doc/uid/TP40007836-SW1

NSDate *today = [[NSDate alloc] init]; 
NSCalendar *gregorian = [[NSCalendar alloc] 
      initWithCalendarIdentifier:NSGregorianCalendar]; 
NSDateComponents *offsetComponents = [[NSDateComponents alloc] init]; 

[offsetComponents setMonth:3]; // one quarter 

NSDate *oneQuarterFromToday = [gregorian dateByAddingComponents:offsetComponents 
      toDate:today options:0];